1. Field of the Invention
This invention relates to a dryer for drying washed glass plates as they travel in a housing, which has a dryer entrance slot and a dryer exit slot and contains a horizontal conveyor for the glass plates, which conveyor comprises and serves to support a bottom edge supporting conveyor and backing elements, which define a plane of travel for the glass plates and serve to support glass plates at one of their broadsides when the glass plates stand on the bottom edge supporting conveyor, which dryer also comprises elongate front and rear blast nozzles, which are respectively disposed in front of and behind the plane of travel for the glass plates and are upwardly inclined opposite to the direction of travel and have air exit slots or perforation lines, which face the plane of travel for the glass plates and extend from a level which is close to the level of the bottom edge supporting conveyor in a direction which is upwardly inclined opposite to the direction of travel, wherein respective shields are provided between the front blast nozzle and the adjacent front wall of the housing and between the rear blast nozzle and the adjacent rear wall of the housing, and wherein the housing is provided with an exhaust air outlet.
Such dryer is required in an insulating glass assembling line, in which the dryer succeeds a washing machine, which serves to wash glass plates as they travel through the machine. The glass plates then enter the dryer and are dried as they travel through the dryer. The dryer and the washing machine are often combined in a unit.
2. Description of the Prior Art
The known dryers comprise a horizontal conveyor, which serves to move the glass plates through the dryer as the glass plates stand on the conveyor and are supported at one of their two broadsides by means of backing elements which generally consist of rollers which are freely rotatable about axles which are transverse to the direction of travel of the horizontal conveyor. Those surfaces of said rollers which contact the glass plates define a common plane, which will be described hereinafter as a plane of travel for the glass plates. This is the plane which is continuous to that broadside at which the glass plates contact the rollers. In the dryer, the plane of travel for the glass plates is a fixed plane that is defined by the backing elements are accommodated in a housing, which has two dryer end walls which cross the direction of travel of the horizontal conveyor and which are respectively formed with an entrance slot and an exit slot for receiving and delivering the glass plates. Said slots are aligned with the plane of travel for the glass plates.
The housing also contains two elongate blast nozzles, which are respectively disposed in front of and behind the plane of travel of the glass plates. The air exit slot or perforation line of each blast nozzle extends substantially parallel to the plane of travel of the glass plates and rises from a level which is close to the level of the bottom edge supporting conveyor in which a direction which is upwardly inclined opposite to the direction of conveyance. The air exit slots of the blast nozzles are so oriented that they direct an air stream opposite to the direction of travel toward the plane of travel for the glass plates at an oblique angle to said plane so that each broadside of each glass plate which is conveyed by the horizontal conveyor will initially be contacted by the air from the adjacent blast nozzle at the leading upper corner of the glass plate and will then be swept by a front of blast air in a progressively increasing area, which depends on the inclination of the exit slot or perforation of the blast nozzle, until the plate is finally contacted by the air blast at the trailing lower corner of the glass plate so that said corner is the last portion of the glass plate at which said plate is dried. As a result, any water droplets disposed on the glass plate are urged by the air streams in a downwardly inclined direction opposite to the direction of travel of the glass plate. To ensure that the streams of humid air cannot contact that portion of the glass plate which has already moved past the two blast nozzles, a shield is provided between each blast nozzle and the adjacent front or rear wall of the housing. That shield may consist of a rubber lip, which is secured on one side to the blast nozzle to extend along the same whereas the other longitudinal edge of the rubber lip contacts the adjacent forward or rear wall of the housing.
The air which hast been discharged by the blast nozzle must be able to escape from the housing of the apparatus. That air could not escape at the bottom of the housing because the bottom edge supporting conveyor and a water-collecting tub are provided at said bottom. The exhaust air must not and cannot leave the housing in the direction of travel because in that case the exhaust air would remoisten the dried glass plates. It is also impossible to discharge the exhaust air from the housing opposite to the direction of travel because the washing machine is provided at the entrance end of the housing. It is not desirable to discharge the exhaust air at the front side of the housing because in that case the exhaust air would be blown against the operators and because it is desired to cover said front side with glass panes on a large area so that the drying operation can be watched and checked at any time. In the known dryers the exhaust air cannot be conducted through the top wall of the housing because that top wall cannot be provided with an outlet for exhaust air. This is due to the fact that the blast nozzles of the known apparatus terminate only a small distance from the entrance wall of the dryer so that there would be no space for an exhaust air outlet in the region between the top end of the two blast nozzles and the entrance end wall, particularly because the pipes for supplying air to the two blast nozzles occupy a certain space and open into the blast nozzles from above in that region. That portion of the housing top wall which in the direction of travel succeeds the upper end of the blast nozzles cannot be provided with an exhaust air outlet because said portion of the top wall overlies that dry compartment of the housing which is separated by the shields from the wet compartment near the entrance. The air stream does not and should not enter that dry compartment. For this reason the rear wall of the housing of the known dryer has been formed with a bulge, which constitutes a vertical duct for the exhaust air so that the air discharged by the rear blast nozzle can easily enter said exhaust air duct. But the known dryers have the disadvantage that the air discharged by the front blast nozzle can reach the exhaust air duct only with difficulty because that air discharged from the front blast nozzle initially flows in a downwardly inclined direction and must then be deflected to flow across the top edge of the glass plate into the rear region of the housing. The difficulties which arise from that necessity increase with the height of the glass plates which are to be dried because an increase of the height of the glass plate will result in a decrease of the flow area which is defined by the entrance end wall of the housing, the top wall of the housing, the blast nozzles and the top edge of the glass plate and through which the air can flow into the space behind the glass plate. As a result, high glass plates cannot be dried as effectively as small glass plates so that the drying of high glass plates takes much more time.